Dental filling materials have evolved from metallic fillings to porcelain compositions, and more recently to light-curable resin and filler blends. Of the light curable resins currently available, resins having cross-linkable methacrylate groups are preferred. Methacrylate resins may be blended with a filler and applied to a cleaned cavity. The resin is then light cured with a light source which provides an appropriate frequency so that monomers in the resin/filler blend crosslink to form a polymer network.
The resin/filler blends provide excellent biocompatibility, are extremely long lasting and are easy to handle. The blends are also inexpensive and are easily prepared.
Some of the more recently used methacrylate resins are bis-phenol A diglycidol methacrylate (bis-GMA), urethane dimethacrylate (UDMA), and polycarbonate dimethacrylate (PCDMA). Often, one or more of the above-identified resins is diluted with, e.g., triethylene glycol dimethacrylate (TEGDMA) or ethylmethacrylate (2-HEMA). The resin component is then mixed with fillers such as silicates, until a desired viscosity or optimal physical properties are achieved.
The resin/filler composites are useful in many dental restorations. These composites are designed to approximate natural tooth structure and are sometimes provided in kits which also include gray and yellow dyes so the restoration can be shaded to closely match the surrounding dentition.
U.S. Pat. No. 4,433,959 discloses a composite laminate dental veneer which includes color pigments of a dentin color blend. The coloring system enables the materials to closely approximate the appearance and color of a natural tooth. Tooth enamel and dentin colored blends are provided. Like other tooth-colored dental composites, the materials cannot be used to match the gum tissue of a patient as the material is white in color with shades of yellow and gray.
U.S. Pat. No. 4,521,193 discloses a method and kit for constructing dentures. The dentures include tooth-colored acrylic areas and gingival-colored acrylic areas. The temporary one-piece acrylic denture does not restore the appearance of a natural gum line but rather is used as a prosthesis.
To restore an injured tooth, a carious lesion is drilled out and the tooth is prepared to receive restorative material. A bonding agent is applied to the prepared surface and allowed to bond to the enamel and dentin. In more recent restoration kits, a light curable bonding agent is applied to the clean surface and light cured. A dental composite material is then applied to or inserted in the cavity preparation and light cured to form a restoration.
Class V cavities are those appearing on the gingival third of the facial and lingual surfaces of all teeth. Class V cavities include those at and beneath the gum line. Gum recession may occur in these areas reducing the natural gum line. Because many of these cavities appear where a patient's gums should be, it is desired to provide a gum-colored dental composite for filling cavities at or beneath the gum line. To the best of applicants' knowledge, a gum-colored dental composite has not yet been developed.
In elderly people and those suffering from periodontitus, receding gum lines have the effect of making teeth look longer by extending the clinical crown. It is desired to provide a gum-colored dental composite which can be used on the gingival third of a tooth to cosmetically restore the appearance of the natural gum line to where it was before recession of the gums occurred. Likewise, it is desirable to provide a gum-colored dental composite which can be used to cosmetically improve the appearance of a damaged gum line by its application to the gingival portion of a cavity preparation or directly onto the tooth.